Effect of rifampin on immunity to tuberculosis and on delayed hypersensitivity to purified protein derivative.

Mice vaccinated with mycobacterial ribonucleic acid (RNA) produced a high immune response and did not develop delayed hypersensitivity to purified protein derivative (PPD), and rifampin had no effect on the immune response. Mice vaccinated with viable H37Ra cells produced a high immune response and did develop delayed hypersensitivity to PPD. Rifampin had no effect on this immune response, but reduced the footpad reactions to PPD. Both mycobacterial RNA and poly(A:U) served as adjuvants for induction of hypersensitivity to PPD. This hypersensitivity was reduced by the administration of rifampin. Rifampin had no effect on the production of mycobacterial growth inhibitory factor, which is produced following vaccination of mice with mycobacterial RNA or viable H37Ra cells. Rifampin had no effect on the nonspecific phase of the granulomatous response, but did inhibit the secondary allergic phase of this response. The action, therefore, of rifampin that inhibits the induction of delayed hypersensitivity but had no effect on the immune responses against tuberculosis leads to a separation of tuberculin hypersensitivity from cellular immunity to tuberculosis.